Package build failed for UI extension

Package build failed for UI extension

REQUIRED INFORMATION

Sencha Cmd version(s) tested:

Sencha Cmd v4.0.1.45

Operating System:

OSX 10.9

Framework used:

Sencha Architect 3.0.0

Sencha Touch 2.3.1

Description:
I've made an UI extension for Architect 3.
I can use the extension inside architect, but I must include the extension package in app.js to build my app with my extension.
The app doesn't build since I don't build the extension, but building the package give me an error:

NOTE: In older versions of Sencha Cmd, sencha package build may fail if you have Sass that depends on the theme. To workaround this limitation, you can set the skip.sass and skip.slice properties in ".sencha/package/sencha.cfg". The package will be usable in an application because the theme will be included in sencha app build.

After a brief search I've added in sencha.cfg the following lines:

Code:

skip.sass=true
skip.slice=true

After that the package has built.
It seems that this bug is not only in older version of Sencha Cmd.